As discussed in Patent Literature 1, for example, high efficiency of a refrigerant compressor such as a scroll compressor is achieved by supplying a portion or all of refrigerating machine oil (hereinafter referred to as oil) used for lubricating bearings to a compression chamber which reduces leakage in the compression chamber. However, in the refrigerant compressor discussed in Patent Literature 1, the amount of oil supply cannot be adjusted when the compressor is operated, since the amount of oil supply to the compressor is determined by a fixed restriction provided on the oil supply line.
As discussed in Patent Literature 2, such refrigerant compressor is known in which a valve, which opens and closes the oil supply line, is provided along the oil supply line, and by the pressure difference between a high pressure portion and a low pressure portion, the valve opens and closes and varies the restriction on the oil supply line by two stages. In this manner, the amount of oil supply is adjusted.
Further, as for a refrigerant compressor used in a refrigerating apparatus including a hydraulic screw compressor or an air conditioning apparatus for a vehicle, it is known that the oil separated from a discharged refrigerant gas in an oil separator connected to a discharge side of the compressor is injected to the compression mechanism with the flow rate adjusted from the outside (e.g., see Patent Literatures 3 and 4).